Irrigation: Irrigation regulation
FROM TLC Staff |
January 1, 2007
For years, landscaping companies have installed and maintained time-based irrigation system controllers. But what if a monsoon swamps a section of the country? Most irrigation systems still water based on their internal timer. The fact that the turf they’re irrigating won’t need water for another week or so doesn’t enter the picture. As a result, the system wastes water and over-irrigates the lawn. But new technology, in the form of smart irrigation controllers, is changing that.
Their introduction is timely: New legislation in California, AB 1881, is setting higher landscape water conservation standards throughout the state by 2010. And other cities and states are considering similar legislation. With the new standards comes the requirement to use smarter irrigation controllers, and that means business for you. Residential and commercial property owners will rely on landscaping companies to install these systems to meet the new water conservation expectations and water budget allocations.
According to the Virginia-based Irrigation Association, a nonprofit organization focused on water conservation, “smart” sprinkler controllers use compact electronic control modules to reduce outdoor water use by monitoring and acting on pertinent information about site conditions such as moisture, rain, wind, slope, soil and plant type. Taken together, these conditions, act in a process known as evapotranspiration, or ET.
This is the process by which soil loses water through water evaporation and transpiration from plants. Ideally, to avoid irrigating too much or too little, you want to know 100 percent of all ET taking place in a plot of soil. However, knowledge of a lower percentage will still save your clients money.
According to Rob Starr, head of strategic technologies for Toro Irrigation, the most accurate way to receive precise ET data pertaining to the site is to have a real weather station on the property, like many golf courses do. But weather stations can cost $10,000 or more, and not many customers want to spend that kind of money. The next best – and most cost-effective – irrigation control method is an ET controller.
ET controllers work well when installed on residential and stand-alone commercial sites, but because this technology is new, there is some resistance now from customers. According to Tom Penning, president of ET controller manufacturer Irrometer, it’s a matter of cost-effectiveness. “A lot of residential clients might not be willing to spend the money for the controller or the signal fee each month, especially with homes changing hands every few years.”
In response, you have to explain the advantages of these systems to your customers. “An ET controller is going to save them money because it is conserving water,” says Aaron Hauck, electronics product manager for Nelson Turf. “Sites that have used ET controllers experience a healthier landscape because they are not over watering. With over watering, you can get fungus issues or you can push fertilizers past the root mass into the ground water.”
Controllers paint a complete moisture picture
According to Susan Basch, senior product manager at Rain Bird, economics, the price of water and the size of the area to be watered are the primary factors determining what type of ET controller you’ll want to use to irrigate a site. “For larger, more complex sites, the closer you can get to 100 percent ET, the better,” Basch says. “For smaller sites, 80 percent to 90 percent ET might be close enough.”
There are two variations of ET controllers:
- The first type receives weather data for a particular area from a national or onsite weather station. Factors such as temperature, humidity, rainfall, transpiration and solar radiation are computed to get an average of how much water the landscape being monitored needs.
- The second type depends on soil moisture sensors buried in the ground to tell it when the landscape needs to be watered based on the level of moisture present in the root mass. These controllers can be used in conjunction with weather station information to gain a more complete moisture “picture” of a site.
The concept of compiling ET data from weather stations has been around for years. It began with the agricultural industry in an effort to lower irrigation costs and protect crops from over watering.
Using similar parameters, Rain Master Irrigation Systems’ iCentral Web-based controller’s ZipET program collects local weather information, assimilates the data and organizes it by ZIP code, then sends the individual ZIP code information daily to its users’ irrigation sensors.
“You never have just one weather station within any ZIP code,” explains Steve Springer, vice president of marketing business development for Rain Master. “When you take the averages across the area, you get a highly accurate measurement of soil moisture requirements.”
Web-based controller systems allow landscapers to log onto a Web browser anywhere in the world to check irrigation systems on any property and make changes if needed. They can also receive alerts on their cell phones. Rain Bird’s ET Manager is one such system. It calculates ET based on weather station data, which can be manipulated by the site owner or a third party operating the weather station.
Soil moisture sensors and weather data give the most complete picture possible
Soil moisture sensors that are buried in the ground measure the amount of water in the soil and relay that information to an irrigation control system. To properly deliver irrigation with a time-based controller, Penning suggests watering be broken into several distinct start times to better check the soil content data and decide whether the water should be delivered.
“Soil moisture sensors don’t turn the water off; they simply decide when to turn water on,” says Penning. Suppose, for example, you have an irrigation system set to water in three 20-minute increments. If, after one or two cycles, you have enough moisture, it will eliminate the third cycle. “As a bonus, the system automatically adjusts for different seasons when the irrigation demand is not as great,” Penning adds.
When used with an ET controller, the soil moisture sensor will tell the controller when to irrigate, and the ET data will say how much to apply based on the weather data collected from the weather stations. “The controller doesn’t really know how wet the soil is,” Penning says, “only what theoretically transpired. They work in conjunction very well.”
Penning says it is important to consider what type of landscape you are irrigating. For turf grass, you’ll only need one sensor because the root systems are all shallow. But for large shrubs and trees, you’ll need to install multiple sensors – shallow and deep – to ensure that the entire root system gets adequate irrigation.
According to Basch, soil moisture sensors need to have the following aspects: affordability, reliability and accuracy, and be maintenance free. “It’s unlikely that someone will be available or willing to do regular maintenance on something that’s buried in the ground,” Basch says.
An alternative to conventional soil moisture content monitors is Irrometer’s Watermark sensor system. Watermark is a resistive-type sensor that measures soil-water tension, or how much tension the plant is using to extract moisture from the soil. The sensor absorbs water from the soil and releases water as the soil dries; electrodes measure the difference in resistance when the soil is wet compared with when it is dry. Unlike other sensors, Watermark doesn’t have to be “site calibrated.” The tension is measured internally in the device to tell how much moisture is available to the plant.
If you’re in the market
All manufacturers agree that smart controllers are more complex to install and more expensive up front. But once the product is installed and operating correctly, it should not require maintenance. “Ideally, you won’t have to think about it for the life of the product,” Basch says.
“ET controllers can’t fix bad irrigation systems,” cautions Hauck. “An irrigation system has to be installed correctly for the ET controller to work.”
Many companies offer software to make the setup process easier. The landscaper can do all of the initial programming on a laptop and download it to an ET-based controller. “We all understand that a landscaper’s time is money,” Basch says. “The sooner he can complete a job, the better.”
According to Starr, builders really like ET controllers because they reduce over watering, thereby reducing mold and jobsite pollution through water runoff. And aside from water bill savings for property owners, ET controllers provide better landscaping. “It’s like having a hotline to Mother Nature,” Starr says. “Once you set it, you never have to come back and touch it again.”